The present invention relates to a method for making carbon dioxide snow and to an apparatus therefor. More particularly, the present invention relates to a method for making snow-like dry ice by subjecting liquefied carbon dioxide to adiabatic expansion and to an apparatus therefore.
Carbon dioxide (CO.sub.2) snow is employed widely as such or in the form of dry ice blocks formed by hardening such snow for refrigerating drinks and food or for keeping them fresh. CO.sub.2 snow is made by injecting liquefied CO.sub.2 through a nozzle into a cylinder, called a snow horn, having an opening at the lower end to effect adiabatic expansion.
Apparatuses having various structures have been proposed so as to make CO.sub.2 snow efficiently. For example, Japanese Utility Model Publication Nos. Sho 56-3309 and Sho 56-3310 describe apparatuses employing nearly cyclone-shaped snow horns to which liquefied CO.sub.2 is injected in tangential directions of the snow horns, respectively. Japanese Unexamined Patent Publication No. Hei 6-257937 describes an apparatus in which liquefied CO.sub.2 is injected from a nozzle protruding into a snow horn to form spiral flows. Japanese Unexamined Patent Publication No. Hei 6-298513 describes a structure in which liquefied CO.sub.2 is injected from a nozzle disposed to oppose an injecting section protruding into a snow horn. U.S. Pat. No. 4,911,362 describes an apparatus having a pair of snow horns which are arranged to form a Y shape.
However, these CO.sub.2 snow making apparatuses are designed to obtain dry ice having properties suitable for freezing food and the like and are directed to achieve improvement in the yield of dry ice, reduction of noises, etc. Accordingly, the dry ice obtained assumes a form of small snowflakes, so-called powder snow.
Meanwhile, when snow is allowed to flow artificially as a scenic effect in various events and attractions, the artificial snow is desired to stay in the air as long as possible and is of snowflakes which can flutter so as to be impressive to viewers. However, the artificial snow made according to the prior art is mainly directed to be deposited on slopes of skiing areas and the like, so that the conventional techniques of making artificial snow cannot give fluttering artificial snowflakes which appeal to viewers. Further, the CO.sub.2 snow made by any of the prior art CO.sub.2 snow making apparatuses is of small snowflakes. Accordingly, if such artificial snow is employed in an event and the like, it has poor visual effect and stays in the air too short to give sufficient scenic effect. For such reason, when a snowy scene is to be produced in an event and the like, for example, soap bubbles, styrofoam and confetti have been employed as substitutes for snow.